What is the primary function of a seatbelt in a vehicle?

The primary function of a seatbelt in a vehicle is to keep occupants safe during a collision. Seatbelts are designed to restrain the body's motion in the event of a sudden stop or crash. By securing occupants in their seats, seatbelts help prevent them from being thrown forward or ejected from the vehicle, which can significantly reduce the risk of severe injury or death.

In addition to their role in protecting passengers from the forces of a crash, seatbelts also work in conjunction with airbags to provide a more comprehensive safety system. When a vehicle experiences a collision, the seatbelt ensures that the occupant is properly positioned to benefit from the airbag deployment, which further enhances safety.

The other options do not accurately capture the primary purpose of seatbelts. While comfort might be a secondary effect of seatbelt use, it is not their main function. Similarly, seatbelts do not contribute directly to fuel efficiency, nor do they play a role in stabilizing the vehicle's position during operation. The emphasis on safety during collisions is what fundamentally defines the critical role of seatbelts in vehicles.